Influence of Environment 241 



The part played by these different factors of development may 

 be graphically illustrated by the accompanying diagram (Fig. 88), 

 in which the base line represents heredity and the other lines rep- 

 resent the extrinsic factors of environment and education. For 

 each individual heredity is a constant factor but environment and 



Heredity 



FIG. 88. DIAGRAM TO SHOW THE INFLUENCE OF HEREDITY, ENVIRONMENT 

 AND TRAINING IN THE DEVELOPMENT OF AN INDIVIDUAL. Various types 

 of individuals (represented by the triangles) may be produced from the 

 same germ cells (heredity) if the environment and training are variable. 



training are variables. With a given heredity the characteristics 

 of the developed organism may vary enormously depending upon 

 the extrinsic factors. Hereditary possibilities are not changed by 

 accidents of environment but development is so changed. After 

 the fertilization of the egg the hereditary potencies of every organ- 

 ism are unalterably fixed but the extrinsic factors remain variable 

 and may be controlled. 



All of our social and ethical institutions such as government, 

 education and religion deal only with extrinsic factors of develop- 

 ment and of life. Nevertheless there is no evidence that such 

 extrinsic influences ever modify heredity, no evidence that the 



